Ureter

The ureter is a paired fibromuscular tube that conveys urine from the kidneys in the abdomen to the bladder in the pelvis. 

Gross anatomy

The ureter is 25-30 cm long and has three parts:

1. abdominal ureter: from the renal pelvis to the pelvic brim
2. pelvic ureter: from the pelvic brim to the bladder
3. intravesical or intramural ureter: within the bladder wall

Course

The ureter begins its descent to the bladder by running along the medial aspect of the psoas muscle. Here, the ureter lies anteriorly and slightly medial to the tips of the L2-L5 transverse processes. 

It enters the pelvis anteriorly to the sacroiliac joint at the bifurcation of the common iliac vessels (at the pelvic brim) and then courses anteriorly to the internal iliac artery down the lateral pelvic sidewall. 

At the level of the ischial spine it turns forward and medially to enter the posterolateral wall of the bladder, where it runs an oblique 1-2 cm course, before opening into the bladder at the internal ureteric orifice ^1-2.

Relations

The relations of the ureter are somewhat complex due to the differences between the left and right sides of the abdominal cavity and differences between male and female pelvic viscera.  

Abdominal ureter

Following the course of the ureter from superior to inferior ^1-2: 

• posteriorly: psoas muscle; genitofemoral nerve; common iliac vessels; tips of L2-L5 transverse processes
• anteriorly
  • right ureter: descending duodenum (D2); gonadal vessels; right colic vessels; ileocolic vessels
  • left ureter: gonadal artery; left colic artery; loops of jejunum; sigmoid mesentery and colon
• medially
  • right ureter: IVC
  • left ureter: abdominal aorta, inferior mesenteric vein

Pelvic ureter

• posteriorly: sacroiliac joint, internal iliac artery
• inferiorly
  • male: seminal vesicle
  • female: lateral fornix of the vagina
• anteriorly
  • male: ductus deferens
  • female: uterine artery (in the broad ligament)
• medially
  • female: cervix

It should be noted that the only structures to anteriorly pass over the pelvic ureter is the ductus deferens in males and the uterine artery in females. 

Constrictions

The ureter has a diameter of 3 mm ¹ but there are three constrictions, which are the most common sites of renal calculus obstruction:

• at the pelvi-ureteric junction (PUJ) of the renal pelvis and the ureter
• as the ureter enters the pelvis and crosses over the common iliac artery bifurcation
• at the vesicoureteric junction (VUJ) as the ureter obliquely enters the bladder wall

Blood supply

• arterial supply: from branches of the renal artery, abdominal aorta, superior and inferior vesical arteries
  • some texts also include supply from the gonadal, middle rectal and uterine arteries ^1-2
• venous drainage: via similarly named veins but is highly variable ^1-2

Lymphatic drainage

• abdominal ureter: aorto-caval and common iliac nodes
• pelvic ureter: internal and external iliac nodes ¹

Innervation

• derived from renal, aortic and hypogastric autonomic plexuses ¹

Histology

The ureteric wall is composed of three layers (from outside to inside):

1. adventitia
2. smooth muscle
3. transitional cell epithelium ¹

Variant anatomy

• duplex collecting system
• bifid ureter
• ectopic ureter
• ureterocoele

Related pathology

• transitional cell carcinoma of the ureter
• ureteritis
• ureteric calculi